1. Technical Field
This invention relates to pest repellers, and relates more particularly to devices for broadcasting electronically-generated ultrasonic sound waves at a high volume to repel household pests, particularly rodents.
2. Discussion of the Prior Art
Household pests, such as mice, rats and the like, are a common problem, both domestically and commercially. Attempts to deal with the nuisance caused by these pests include the use of snap-traps that, unless located in protected areas can be harmful to children and pets, and insecticides, both liquid and powder, some of which include dangerous poisons. Notwithstanding these age-old solutions, mice and rats continue to multiply and thrive.
Rather than capturing or killing rodents, products have been marketed which simply repel these pests, causing them to avoid or leave areas that might otherwise attract them, such as kitchen cupboards, pantries or basements. Commercially available ultrasound transmitters emit sound waves with frequencies generally too high to be heard by the human ear, but high enough to annoy or repel rodents, directing them away from areas which they tend to frequent, and possibly toward areas where they can more readily and safely be trapped or otherwise eliminated.
Ultrasonic sound is highly directional and will be reflected by hard surfaces. Ultrasonic sound waves act more like light than sound from a radio. The waves travel from a transducer in a cone-like shape and leave “shadows” behind objects in their path, such as furniture, curtains or the like. The shadows are areas of non-coverage.
Products currently in the market are of two general styles, “direct plug-in” and “table top”. The cone-shape emitted from the transducer covers approximately 120°. The direct plug-ins are limited in their useful coverage area because of the fixed relationship between the electrical connection used to power the unit from household current, and the sound producing transducers. Effectively, the useful coverage is dictated by the location of the wall outlet and the existing objects in the room.
The table top versions contain an electrical cord and plug and, inherently, have more potential for useful coverage because they can be positioned by the consumer to avoid obstructions that may be present if the unit is plugged directly into a wall outlet.
Dual transducer (speaker) units have been marketed to further increase the useful coverage in both direct plug-in and table top models. These units employ two positionally fixed, side-by-side, transducers positioned generally at about 30° from each other. Such units provide, effectively, 150° of coverage since the areas of overlap have no more effective sound than a single covered area because the amplitude or volume properties, measured in decibels, of the sound waves are not additive. Thus, the net effect of adding the second fixed transducer to the unit is only, on the order, of about 30° of extra coverage.
It would be highly desirable to provide an ultrasonic pest repeller having substantially increased coverage potential without taking up significantly more room, and with little or no additional cost.